How to structure object in javascript

Question

How can I structure an object to allow for initialization the same way as the stripe API:

var stripe = require("stripe")(
  "sk_test_BQokikJOvBiI2HlWgH4olfQ2"
);

I have tried this

var example = (function () {
    function example(api_token) {
        this.token = api_token;
    }
    example.prototype.getSelf = function (callback) {
        //do stuff
    };
    return example;
}());
module.exports = example;

but I get a Cannot set property 'token' of undefined error when calling var sdk = require('./Example')(API_KEY);

Answer 1

Since your function isn't being called as a constructor (via the new keyword), you need to make sure the function you provide doesn't expect to be called that way.

You could do this:

function Example(api_token) {
    this.token = api_token;
}
// ...prototype, etc.

function example(api_token) {
    return new Example(api_token);
}
module.exports = example;

Or don't use a constructor function at all, and use Object.create :

var exampleProto = {
    getSelf: function() {
       // ...
    }
};
function example(api_token) {
    var o = Object.create(exampleProto);
    o.token = api_token;
    return o;
}
module.exports = example;